Interlayer Transport in Bilayer Quantum Hall Systems

Bilayer quantum Hall systems have a broken symmetry ground state at filling factor $\nu=1$ which can be viewed either as an excitonic superfluid or as a pseudospin ferromagnet. We present a theory of inter-layer transport in quantum Hall bilayers that highlights remarkable similarities and critical differences between transport in Josephson junction and ferromagnetic metal spin-transfer devices. Our theory is able to explain the size of the large but finite low bias interlayer conductance and the voltage width of this collective transport anomaly.